This invention relates to oligoethylenepiperazines and their derivatives as well as to methods for the preparation and use thereof.
Several polyalkylene piperazines are known as intermediates for the preparation of polymers and fine industrial chemicals, e.g., surfactants, corrosion inhibitors, wetting agents, detergents, flocculating and/or dispensing agents, veterinary antihelminthic agents, and monomers which polymerize by condensation with various comonomers reactive with the secondary amine function, e.g., alkyl and aryl diisocyanetes and alkyl and aryl diacid chlorides.
Polymeric cations are widely used as anion exchange resins, electron conductors, wetting agents, etc. The "Dowex" synthetic ion exchange resins are prepared from styrene-divinylbenzene copolymers having a large number of ionizable or functional groups attached to this hydrocarbon material by ring substitution. The "Amberlite" ion exchange resins are a series of various crosslinked polymers in bead form which are widely used industrially. Both of these types of anion exchange resins are generally characterized as styrene and polysulfonic acid types bearing aines in the side chains. Anion exchange polymers or oligomers having cationic amines in the main skeletal chain are more stable than the above two types of resins to heat and alkalis. They are also advantageous ion exchangers since they have no unsaturated radicals which exert undesirable adsorption.
4,4'-DISUBSTITUTED-1,1'-ETHYLENE DIPIPERAZINES AND THEIR SALTS HAVE BEEN DESCRIBED IN U.S. Pat. No. 2,756,231 as useful antispasmodics and gastric inhibitors which are prepared by reacting a 1-substituted piperazine with a vicinal dihaloalkane in the presence of a suitable base. The ethylene linkage bridging the two piperazine rings in these compounds is mono - or disubstituted, and the compounds themselves are viscous oils.
Piperazine-containing polymers containing C.sub.3 to C.sub.12 polymethylene radicals bridging the piperazine rings have been described in U.S. Pat. No. 3,532,646. These oligomers are prepared by the polycondensation of an N,N'-bis-.beta.-hydroxyethyl diamine with ring-formation dehydration; this process is inapplicable to ethylene groups, as only hydroxyethylpiperazine is formed. The compounds prepared according to the aforementioned U.S. Pat. No. 3,532,646, represent a mixture of compounds of varying molecular weight. Because of difficulties in separation into each component compound, they are poorly suited as an intermediate for further practical chemical preparations.
Certain polamines containing repeating ethylene-piperazine units in the molecule can by synthesized by the ring-opening polymerization of triethylenediamine (1,4-diazabicyclo-2,2,2-octane) with the aid of an arylsulfonylchloride initiator, as has been described in H. K. Hall, Jr., J. Org. Chem. 28:223 (1963).
As with most polymerization reactions, this ring-opening process continues progressively to form predominantly polymers having relatively high molecular weights, and the resultant product invariably comprises a mixture of many different oligomers. Because of these drawbacks and the difficulties of separating the polymer product into a particular molecular weight component, these products are of only limited value as starting materials for the synthesis of further compounds therefrom.
Since compounds of this class have a wide variety of potential applications, it would be highly desirable to have available a method whereby low molecular weight ethylenepiperazine oligomers could be prepared in such a way as to tailor the molecular weight of the final product to desirable lower values than are obtained by this condensation polymerization method. The present invention fills such a need.